Abstract: A method and apparatus for providing a recent set of replicas for a cluster data resource within a cluster having a plurality of nodes. Each of the nodes having a group services client with membership and voting services. The method of the present invention concerns broadcasting a data resource open request to the nodes of the cluster, determining a recent replica of the cluster data resource among the nodes, and distributing the recent replica to the nodes of the cluster. The apparatus of the present invention is for providing a recent set of replicas for a cluster data resource. The apparatus has a cluster having a plurality of nodes in a peer relationship, each node has an electronic memory for storing a local replica of the cluster data resource. A group services client, which is executable by each node of the cluster, has cluster broadcasting and cluster voting capability.

Abstract: A database schema for storing application data in a relational database backing store of a directory service. The application data has at least some entries with multiple value attributes. According to the invention, the application data is profiled to determine how it may be optimally stored in the backing store. Preferably, single entries having single value attributes are stored in a merged attribute table, while entries having multiple value attributes are stored in per attribute tables. According to the optimization, a majority of the attributes are single valued and are stored in the merged table, and the per attribute tables thus store a relatively smaller number of exceptions. This database schema enhances processing of conventional directory service queries into the backing store.

Abstract: Within a computer cluster usage reference counts are maintained for replicated databases within a computer cluster using cluster membership and cluster voting services. Such a method includes the maintaining of a local reference count for all open distributed data resources within a given node, tracking by a group services client of those nodes that have the open distributed data resources, and using cluster membership services to update the local reference counts for node failures.

Abstract: A generic semaphore supporting semaphore operations from multiple operating systems concurrently. Operating system semaphore invocations are transformed into a generic semaphore API that enables implementation of the semaphores. The generic API enables modification to the semaphore value depending upon the current semaphore value, and enables the queuing of threads to enable waiting upon semaphore operations. The semaphore operations implement synchronization of resource access and synchronization of process or thread execution. The generic semaphore enables applications for specific operating system personalities to execute on a microkernel system without modification of the application semaphore logic. This enables application programmers to code applications using known semaphore operations without regard to their final execution location.

Abstract: A method of hierarchical LDAP searching in an LDAP directory service having a relational database management system (DBMS) as a backing store. The method begins by parsing an LDAP filter-based query for elements and logical operators of the filter query. For each filter element, the method generates an SQL subquery according to a set of translation rules. For each SQL subquery, the method then generates a set of entry identifiers for the LDAP filter query. Then, the SQL subqueries are combined into a single SQL query according to a set of combination rules chosen corresponding to the logical operators of the LDAP filter query.

Abstract: A method of hierarchical LDAP searching in an LDAP directory service having a relational database management system (DBMS) as a backing store. According to the invention, entries in a naming hierarchy are mapped into first and second relational tables: a parent table, and a descendant table. These tables are used to "filter" lists of entries returned from a search to ensure that only entries within a given search scope are retained for evaluation. Thus, for example, the parent table is used during an LDAP one level search, and the descendant table is used during an LDAP subtree search. In either case, use of the parent or descendant table obviates recursive queries through the naming directory.

Abstract: Configuration changes are dynamically applied to a cluster multiprocessing system by enqueuing a configuration change event. When the configuration change event is processed, the prior configuration is backed up and each software component applies a relevant portion of a configuration change transaction in an ordered, synchronized manner. Each software component applies its portion of the transaction either by reinitialization or a logged transition operation. If the configuration change transaction fails, the software components roll back the portions, of the configuration change already applied in an ordered, synchronized manner to restore the prior configuration. Multiple events for different configuration changes may be enqueued.

Abstract: A user definable set of event rollup relationships are maintained as a configuration element. Transitive closure of event rollup relationships is checked at the time of specification to detect cycles and prevent runtime errors. When an event to be processed is detected, the event is compared to defined rollup relationships and queued events to determined if the detected event may be rolled up into at least one queued event or vice versa. If the detected event may be rolled up into a queued event, the detected event is not queued. When any of the queued event may be rolled up into the detected event, the queued events are deleted if processing has not already begun.